One and two dimensional symbols, such as barcodes and the like, have become commonplace in modern day society. Such symbols are utilized everywhere from supermarket scanners to postal delivery systems, and in a variety of other fields. In inventory, factory, and other systems, it is often the case that a conveyor belt includes a variety of items that are moved through the field of view of a scanner, so that such items can be counted, inventoried, or processed in some other way.
Such systems, it is important that the symbol to be read, which is usually placed on the side of a package or other reading surface, be quickly read by the scanning system because the items are moving through the field of view relatively quickly. If the scanning system takes too long to read the symbol, the symbol may completely pass the scanning system before the reading operation is complete. This will cause items to be miscounted and the system could not function properly. In most other applications, reading the symbol as quickly as possible is important, a problem increased by the fact that in two dimensional symbols, the lines are usually scanned sequentially.
Another problem with such systems is that ambient conditions, such as lighting conditions and shutter speed used for reading the symbol may change. Such changes may require adjustments to parameters within the optical reading system, such as the integration time. If the adjustment occurs during the reading of a frame, the entire frame must be discarded because it contains mixed data gathered at two different shutter speeds.
It is an object of the invention to provide a system wherein scanning can be accomplished and any changes made quickly enough so that both one of two dimensional barcodes, and other optical symbols, can be read efficiently enough to allow for the foregoing changes to occur.
It is another object of the invention to ensure that a two dimensional symbol is not read in a manner that requires frames to be discarded because conditions changed in the middle of reading the frame.